Genetic Abnormality
by Sirdudemanton
Summary: The Duncan family has a genetic abnormality that gives Teddy a something.
1. Family Rules

The Duncan Family had a weird genetic thing. Every male in the family got a large cock. Guaranteed. With one twist. Not for the males of course. No. For the females. There was a 90% chance that the female members of the family would grow a member upon reaching puberty. Member. Meaning penis. They grew a cock. It replaced the vagina. Pretty much overnight. Doctors weren't exactly sure what caused it. Tests are done every once and awhile. But nothing comes of them.

The other thing this did was make puberty an extremely horny time for everyone. So the Duncan siblings fucked. P.J. fucked Teddy's ass because he had the biggest cock. Teddy fucked Gabe up the ass because Gabe's cock was smaller than hers. For now. Gabe's cock was growing. Soon he would be bigger than Teddy. And he would have Teddy's ass too. Maybe Teddy would even have two cocks up her ass. These were difficult times for Teddy. And it was a very big possibility that Charlie would go through these changes as well. So Teddy recorded video diaries for her about what it's like having a cock.

Teddy and Gabe were currently jerking their cocks together. Up against each other. With lots of lube.

"My cock is still bigger." Teddy says.

"No, they're the same size." Gabe says.

"They're the same size when I can't hold you and butt fuck you anymore." Teddy says. She turns Gabe around. She rubs her lubed cock on her brother's ass. And then pushes in

Gabe sighs. Only a few weeks longer and his cock should be bigger. He'll show Teddy a real ass fucking. But now he's got to take Teddy's cock in his ass. She goes in and out. Fucking his ass. Slowly. Building up speed. It's not that he doesn't like getting ass fucked. It's just embarrassing. He's glad that Jo has never seen him like this. It's embarrassing to be fucked in the ass by your sister. It's embarrassing for your sister to make you cum from anal sex. He'd rather be cumming in her anus. And making her cum.

Just then PJ comes into the room.

"Teddy! There you are." He says. He's naked. He's erect

"What do you want?" Teddy asks. Still fucking Gabe's anus.

"I'm horny. I want to fuck you. What do you think I want?" PJ says.

"I'm a little busy. Can't you see?" Teddy says.

"Ah but I am the oldest. And the biggest. So I get first dibs on pleasure." PJ says.

"Can you let me finish just this once?" Teddy says.

"Nope." PJ says. PJ grabs Teddy and leads her away.

"You better not move from that position." Teddy says to Gabe.

PJ leans Teddy over and take his own lubed up cock and rubs it on her anus. He pushes in. He fucks Teddy. Teddy moans from pleasure. Her cock is still erect. Her balls ache for release. She'd rather have release from fucking Gabe's anus. But she's not going to be able to do that much longer. And she knows that. She's going to try and fuck Gabe's anus as much as she can over the next few weeks. But PJ is obviously going to be a problem.

PJ fucks Teddy's anus harder. The pleasure builds. It builds. Teddy cums. Ropes shoot out from her cock. Fertile loads of cum. Fertile loads she'd rather be shooting up an anus. Fertile loads that her changed biology would rather be shooting up in a girl.

PJ shoots his ropes of cum up Teddy's anus too. Filling her up. He leaves her with cum dripping. Satisfied. Teddy gets up and goes back to her room. Gabe hasn't moved.

"Good boy." She says.

"Fuck off" Gabe says. Teddy shoves her cock up Gabe's anus as fast as she can to shut him up. She pounds his anus. A lot. Very hard. It takes her a long time to cum. Because PJ just made her cum. She makes Gabe cum twice before she herself cums in his anus. She pulls out.

"I'll get you back for all this." Gabe says.

Teddy slaps PJ's cum from her anus on Gabe's face. "Love you too." She says.

Yes, it was a regular day in the Duncan household.


	2. Soon

Teddy was in the middle of a duncan sibling sandwich. It wasn't a very well made sandwich though. Gabe was on the cock end of Teddy, sucking her cock. Teddy was half hanging of the edge of the bed. On top of her face was PJ. PJ was fucking her face.

Teddy was annoyed however. Because before this all happened she was just having her cock sucked by Gabe. She had a throbbing erection and she got Gabe in her room to suck him off. Of course Gabe argued that his cock was bigger now. But that wasn't true. It wouldn't be true even if it was. Because their father would have to approve that Gabe's cock was bigger. And Teddy knew a way that she could get him on her side. And that would at least delay the cock measuring until it was very obvious that Gabe was bigger.

Teddy was the first to cum in this sandwich. She had had Gabe sucking her cock for longer so it wasn't a surprise. Gabe didn't leave though. Teddy didn't hear him leave. She couldn't see that he was jerking off. And he was going to cum on her cock. He did. He spurted his load of sperm onto her soft cock. Then he left. Teddy felt the spurts of cum on her cock and wonder what was going on until she realized what was actually happening. Gabe was jerking off and he had used her cock as a target. How humiliating. She would get him back for this one too.

Teddy would have said something to him if it weren't for the fact that PJ was currently forcing his cock in and out and down her throat.

In and out. In and out. PJ fucked his sister's face until he came. He pulled out and came on her face.

"What the fuck, PJ." Teddy said to him.

"All these years and you're still not used to that. You probably should get used to it quickly. Because pretty soon Gabe will be doing the same thing to your face too." PJ said.

Teddy sighed. Yep. Soon Gabe would be cumming on her face too.

Teddy wanted some more time with Gabe's anus and mouth before that day however. She got from the bathroom one of her father's viagra pills and takes it. She watches porn for a bit to make herself hard. And she makes sure the Viagra has taken effect.

She goes into Gabe's room.

"Gabe, I'm hard again." Teddy said.

"Already?" Gabe asked.

"Yes." Teddy said. "Open up." Teddy said.

Gabe sighed. Teddy put her cock in his mouth. Gabe sucked her cock. Teddy fucked Gabe's mouth. Slowly at first.

Gabe didn't like sucking cock. And soon he wouldn't have to suck Teddy's cock. Teddy would be sucking his cock. And also he wouldn't have to take Teddy's cock up his ass. Gabe would have his cock up her ass.

Gabe figured that Teddy was probably trying to enjoy him on her cock as much as possible. She knew she didn't have much time to enjoy this. Gabe would make sure that he paid special attention to her when the time came. He wouldn't invite Jo over as much. He'd make it so that Teddy would be his only sexual outlet for the next few weeks.

Teddy came in Gabe's mouth. Making him taste her cum. She kept her cock in his mouth, forcing him to swallow and not spit the cum.

"Yuck" Gabe said.

"Don't lie. You love it." Teddy said.

"If I love this. You'll love mine even more." Gabe said.

"If you really love mine we should make an agreement then. I can keep fucking your mouth just so you can get a taste of my sperm." Teddy said.

"No." Gabe said. Teddy slid her cock back into Gabe's mouth. Gabe rolled his eyes. He sucked on Teddy's cock. Not putting very much effort. Teddy obviously could feel this. She fucked his mouth harder than before.

"You know for someone that wants my cum you're not doing a very good job of trying to get it." Teddy said.

Gabe moaned in annoyance. Teddy kept up at fucking his mouth until she came again. Inside his mouth again. Forcing him to swallow it again.

They spent a good few hours like this before Teddy's cock wanted no more. Gabe was quite angry and confused about why Teddy suddenly wanted to go so soon and so often. He couldn't wait to fuck Teddy's ass. He wanted it as soon as possible.


	3. Convincing

Teddy need to get into action right now. She need to delay Gabe. She need to make sure she could fuck his ass as long as possible. She needed to make her father delay the cock measuring. So that night while her father was watching TV Teddy came out to the living room.

With all the fucking she had done to Gabe and the viagra long worn off her cock was soft. Which was good. It made her look more submissive for her father.

She walked into the living room. She watched her father watching the TV for a bit. Then she got her father's attention.

"What do you want?" Her father asked softly and nicely.

"It's more about what I don't want." Teddy said.

"What do not want then?" Her father asked.

"Gabe's cock in my ass and mouth." Teddy said.

"Oh Teddy. You know how the rules work." Her father said to her.

"I know but I'm wondering if you could maybe delay it "

"Teddy delaying the inevitable only makes whatever is going to happen worse."

"But daaaaad" Teddy said.

"And it's only going to make you madder when it happens too." He said trying to be reasonable with his daughter.

"What if I sucked your cock? Would you do it then?" Teddy said.

"Let me get this straight. You're trying to prevent yourself from sucking Gabe's cock by sucking my cock?" he said.

"You're a much more gentle with me." Teddy says.

"You're supposed to be sucking PJ's cock if you have a craving to suck cock." he said.

"PJ is asleep." Teddy said.

"No." he said.

"Please?" Teddy said.

He rolled his eyes. "Fine. But I'll only consider delaying. It's not a guarantee."

"Thank you so much!" Teddy said. She was on her knees in front of her father. She undid his belt. She got his pants down. And his underpants.

She had his cock in her hand. She stroked it. It was hard. She sucked on it then. Sucked on her father's cock. She sucked on it hard. She hoped she could do a good enough job sucking it. So that her father wouldn't only consider. But would let her have her freedom to not be double fucked for longer. Yes it would happen eventually. But she wanted more time with Gabe's anus and mouth.

"We're not supposed to be doing this you know." Her father says. "It's cheating."

"It's not like I've never sucked your cock before" Teddy said after she had a free moment from sucking her father's cock.

"And everytime we weren't supposed to be doing it." Her father said.

Teddy rolled her eyes and sucked again on his cock.

"Don't roll your eyes at me." He said.

Teddy thought about rolling her eyes again. But she was a good girl. Other than the fact that she was sucking her father's cock. And she fucked her brothers. But that was just a part of the family genetics. Constant horniness. They'd rather have incest. They'd rather not have their sons and daughter getting many different girls pregnant all the time. Let them all have each other for pleasure rather than others. And who knows what it would be like if word of Teddy's cock got out. It was a secret only known by medical professionals.

Teddy sucked her father until he came in her mouth. She didn't really like the taste of any cum except her own. But she took it all and swallowed it to improve her chances of getting an extension for her time with Gabe's anus and mouth. It was a big load.

Teddy swallowed it all. And then said "Has it been a while since mom has given you a blowjob?" she teased him.

He shook his head. "No. Our sex life is perfectly fine. You don't have this many kids with a small load of cum."

Teddy went back to her room to go to bed. Her cock was still soft but it seemed like it wanted to get hard. Teddy ignored it and went to sleep. She was tired after all the things that had happened today. Hopefully she had convinced her father enough.


	4. Gabe does it

Teddy got more time. But it wasn't much. But she thought it was a lot longer than it would have been. But now that it was very very very very obvious that Gabe had a bigger cock. It had to be said. It was official. It was said and done. Gabe could fuck Teddy's ass. But Teddy made sure she fucked Gabe's ass a lot. His ass was almost always full of cum. He didn't invite Jo over at all. Because his ass was almost always dripping cum. He didn't want Jo to see that he was his sister's buttfucking boy and toy. And this had a big effect on the next couple of weeks too. Because his butt was so sore. He didn't fuck Teddy at all. He didn't invite Jo over at all. Waiting for his ass to return to normal. Teddy tried to argue that because Gabe wasn't fucking her ass he didn't really want to because Gabe liked having his ass fucked so much. It didn't work. But it was worth a shot.

The day Gabe finally decided he would fuck Teddy's ass had came.

Gabe went into Teddy's room without knocking or saying a warning.

He looked Teddy. "Teddy I'm here to fuck your ass!" Gabe said.

"Oh. Are you now? But it's been so long since you've had any pleasure at all. Do you want me to fuck your ass just so you can have a refresher on how to properly use an ass?"

Gabe laughed. "No Teddy. I don't want my ass fucked." Gabe said.

"Are you sure? You loved it every time!" Teddy says.

"If I loved it every time then you should have no problem loving it every time. Especially since you like having PJ's cock in your ass so much."

Teddy rolled her eyes.

"Come over here." Gabe said. Teddy got up and went to Gabe. Gabe took a look up and down Teddy's body. He turned her around and looked at her ass. He grabbed her ass cheeks.

"What an ass." Gabe says.

"Not as good as yours." Teddy said. Gabe pushed Teddy forward onto her bed. He pushed her down. Her ass was now in the air. Ready for Gabe to fuck. Gabe lubed up his cock.

He pushed his cock into her ass without telling her or anything. Expected. Teddy moaned out as Gabe's cock entered her anus.

"So nice of you to tell me." Teddy said.

"I did tell you. When I came into your room." Gabe said.

Gabe fucked Teddy's anus. Gradually getting faster as he wanted to. Lubing his cock up more. Slipping in and out of his sister's anus. In and out. In and out. Fucking her.

Gabe's cock couldn't handle much more. It was damn nice to be on top. Almost too nice. For his cock it was new. And his cock really wanted to cum. Jo hadn't let him fuck her at all. Not in the ass. And not in the pussy. So this was new. And his cock was already ready to blow inside of Teddy's anus.

"I'm going to cum!" Gabe moaned. He only told her because he was under the influence of pleasure. He was ready.

"So soon?" Teddy asked. He hadn't been going at it for that long.

"Shut up!" Gabe said. Then he blew his load inside her ass. It was a big one. Like really big. He had saved it up. He didn't intend to. But now that he had done that and blew a huge load into his sister's ass he was glad he did. Glad he could fill her anus up with a lot of his cum.

"Ohhh" He moaned out.

"You're a terrible lover. You know that?" Teddy said once Gabe pulled out. "You didn't even make me cum.

"What an ass." Gabe said. He spanked Teddy. He completely ignored what she had just said.

"I think you're the ass." Teddy said to Gabe. Gabe was leaving Teddy's bedroom. "Aren't you going to help me clean up?" Teddy asked.

"Nope!" Gabe said.

"You know Gabe. When I'm old enough to move out I won't have to play by the rules anymore! Your ass will be sorry!" Teddy said. She hoped she did not have to wait that long to fuck Gabe's ass again though.


End file.
